The present invention relates to a stereoscopic projecting apparatus for use in projecting a stereoscopic image which can be stereoscopically observed through polarized viewing glasses.
There is a strong demand for a device which would allow for the stereoscopic observation of an image in X-ray diagnosis techniques.
Blood vessels are distributed within the human heart in a complex manner. For this reason, to perform reliable diagnosis by an angiography, the image of a blood vessel of the heart should be stereoscopically observable.
FIGS. 1 and 2 schematically show a conventional stereoscopic projecting technique. Two cinecameras 2, 4, which are separated by a distance corresponding to the standard distance between a pair of human eyes, are used to take pictures of the same size of an object at the same time. A cinefilm photographed by the left-eye cinecamera 2 is mounted on a left-eye projector 6, while a cinefilm photographed by the right-eye cinecamera 4 is mounted on a right-eye projector 8. Polarized filters 10 and 12, having deflection angles which are perpendicular to each other, are arranged in the optical paths of projectors 6 and 8, respectively. The left-eye image and the right-eye image are projected from their respective projectors 6, 8 and are superposed on a screen 14, through the filters 10, 12. The image on the screen 14 may be observed by a viewer wearing polarized viewing glasses 16 which have left-eye polarized glass 18 having the same deflection angle as filter 10 and right-eye polarized glass 20 having the same deflection angle as filter 12. Thus, the viewer observes the image photographed by cinecamera 2 with his left eye, and observes the image photographed by cinecamera 4 with his right eye, thereby making a stereoscopic observation of the image of an object.
However, the conventional stereoscopic projecting apparatus described above has the following problems. In order that the image of the left eye and the image of the right eye may be projected as superposed on the screen 14, the cinefilm frame feed speed of the two projectors 6, 8 must be the same, and cinefilms for the left and right eyes must be fed in synchronism with each other. However, in general, there is a slight difference between the frame feed speeds of the projectors 6, 8. For this reason, when projection is performed over a long period of time, the left-eye image and the right-eye image do not coincide with each other and stereoscopic projection cannot be performed. For projection over a long period of time, a plurality of cinefilms must be used in succession. In such a case, observation must be interrupted for each cinefilm replacement in the two projectors 6, 8, and for synchronization between the two projectors, preventing ready observation. To avoid this problem, four projectors may be used, with two projectors being started just prior to the time the other two projectors finish projecting. However, it is impractical to use four projectors.